The present invention relates generally to wheel balancing machines. More particularly, the invention relates to a wheel balancer utilizing a calibration technique that requires the user to input only one dimensional characteristic of the tire.
In a conventional electronic wheel balancer, the wheel assembly to be balanced is placed on a shaft that extends laterally from the wheel balancer chassis. The shaft is directly or indirectly coupled to an electric drive motor so that the shaft and wheel assembly mounted thereon can be rotated. Imbalance force transducers responsive to mechanical imbalances in the wheel assembly are mechanically linked to the shaft and motor. These transducers send electrical signals to a processor which performs predetermined mathematical computations in order to analyze the signals.
After the imbalance signals are processed, visual indicators are typically provided to the operator, identifying an amount of compensating weight that should be added to the tire and wheel assembly, as well as identifying a location or locations where correction weights should be attached. Wheel balancers of the prior art are shown and described in U.S. Pat. Nos. 4,423,632 and 5,969,247, both of which are incorporated herein by reference.
Wheel balancers require frequent calibration. In some cases, for example, daily calibration may be required. Traditionally, balancers have been calibrated as a lump system by placing a known weight at a known location in space and measuring the signal output. This requires that the operator correctly enter the wheel diameter, width and offset. Errors in measuring or entering these dimensions are carried forward to all balancing operations.
Traditionally, the assignee of the present application has utilized a two-spin methodology for calibrating a wheel balancer. The calibration tire is spun a first time with no attached weight in order to provide a baseline. For the second spin, a known weight is applied at a known location on the outer plane. Others have used a three-spin calibration, but the entry of all three dimensions (wheel diameter, width and offset) is still required.